I spotted this wonderful display of eggshell planters at the mighty Dynamo Donuts in San Francisco's Mission District. (Note the fresh-from-the-fryer bacon maple apple donuts in the upper left.) Instructables has a how-to on making your own "eggshell seed starters."
David Pescovitz is Boing Boing's co-editor/managing partner. He's also a research director at Institute for the Future. On Instagram, he's @pesco.